Electric alternating-current machine



May 26, 1925.

1,539,662 H. FREI ELECTRIC ALTBRNATING CURRENT MAcHiNE Filed Fb. 13, 1922 z sheets-'sheet 2 Patented May 26, 19,25.

UNITED STATES HEINRicHrRm, or oBRRENGsTRINGEN, NEAR ZURICH, SWITZERLAND.

ELIITC'JRIC LTERNATING-CURRENT MACHINE.

'Appiieationrnied February 13, i922. serial No. 536,269.

To all whom it may comer/n:

Beit known that I, Hummer; Fauna citi- Zen of the Republic of Switzerlandresiding at Obereiigstringen, near Zurich, Switzerland, vhave invented certain new and vuseful Improvements in Electric AlternatingCurrent Machines, of which the following is ka specification, reference being had therein to the accompanying drawing. y

The invention has reference to improvements in electric machines and particularly to` alternating current motors. f

Alternating current y motors are known having two sets of field magnets each of said sets consisting of a plurality of bipolar magnets isolated from each other, the pole pieces of each magnet beinglocatedone ahead of the other considered circumferentially and the single rmagnets of therespective sets being 'so arranged that each magnet of each set yis located in between two a jacent polar projections of thema netsof the other set, coils being provided or ther respective ysets one of which is adaptedfor exciting all the magnets of one set and the other coil for exciting all the magnets of the other set.

Motors of the above mentioned typepresent besides a low electrical eficiency and a low power factor, the principal `disadvantage that in consequence of the arrangement of theindividual magnets these motors could not be designed as three-phase motors. It was further impossible to attaiiisymmetrical production of a magnetic field vin the armature, which featureis absolutely necessar and the magnets of the individual sets being( so located that the heads of thefbundles of sheets of one set of magnets forming the pole faces are located between the headsy of the bundles of sheets Of the other sets.

kThis arrangement enables one `to attain .'ery favorable conditions for three-phase for an economic design of the motor, an for a good utilization of the armature current machines especially for` three-phase motors with squirrel cagerotors. Preferably the rotor is designed as a bell-shaped external rotor, whereby a verygood `cooling eiect is attained. It is further advantageous to have the armature bars fixed to the armature and to short circuit rings by inserting these parts in a casting of a metal such as Y aluminium. f y By means of a simple changing of the pole connections and connecting the coils in parallel a three-phase motor of the above mentioned type may be utilized as a single-phase motor whereby the speed and the output are approximately reduced in the ratio 3 :1.

Constructional examples Yof the object of the invention are illustrated on the accompanying drawings, yin which: n

i Fig. l is a side elevation of. a three-phase motor the upper half of which is shown .in verticalv sections, along lines I-I and lines 1-1 of Fig. 2;

Fig. 2 is a front elevation of the motor, the upper right hand quarter of this -gure being asection along line II-'II of Fig. 1;

Fig. 3 is a developed diagram of the pole face of the inductor having four bundles of sheets for each pole and each phase;

Fig. 4 is an elevation view of the inductor showing the arrangement of the bundles of sheets tour bundles of magnetic sheets being provided for each pole and `each phase;

Figs. 5 and 6 show details of the bundles of dynamo sheets and Fig. 7 is a diagrammatic development of l the pole headsl 14. and 15 of the three magnet sets.

With'the asynchronous motor illustrated in Figs. l and 2, the inductor l is arranged internally and the armature 2 is arranged externally. The casing 3 is built of three parts.. The armature comprises a bell-shaped part 4 to which there is rigidly screwed the armature core of Lmagnetic sheets of lamin, the armature bars and the short circuit rings being united by a metal cast around these parts. The bell-shaped part 4 is rigidly secured to the shaft 5, so that the armaturerevolves with the rotating shaft 5.

The stator forming the inductor consists -mainly ofthree concentric ring coils 6", 6b,

6, located within packets or bundles of magnetic sheets 7a, Tb and 828", the ring coilsy being held in the proper position by the means described hereinafter. Each of the ring coils consists of the coil body 9 of a U-Shaped radial cross-section made of insulating material 'of a suiiiciently high mechanical resistance in which body the insulated material for instance the wire or the like for providing for the required ampereturns is placed by being wound up into the trough formed by the fcoil body. The -U- shaped ring 9 is then closed by a cylindrical cover of insulating material. The packets of magetic sheets 7, 7b and 8a, 8b are composed of a number ot sheet elements, which are 'illustrated in elevation in Figs. 5 Vand 6, whilst Fig. l showsthe packets in 'position in 4a side view. Each sheet element is made of 'one piece and consists of an inner part 10 with two 1Shanks 11 and i12, the former being AShorter than the latter. The shanks 11 and 12 are provided with extensions `1li, 157 a tree space 16 is present in the centre. Notch'es 17 rare provided on the sheet elements. rPhe shanks 12 are bent either to the lett or to the right oli' the lines indicated by dots in Figs. '5 and G so that shapes are formed as illustrated in Fig. d. According to the number of pole pieces the shank 12 is made longer or shorter and 'is bent through a Alarger `er smaller angle with respect to the shank 11. In the constrnctionall torni il1ustrated in Fig. i an eight pole motor is shown. By v `the `combination ot' similarly shaped sheet elements, which may be suitably isolated, packets of sheets T, 8, and 7b, S" respectively yare provided which are formed symmetrically but extending in opposite directions. A plurality ot sheet elements illus trated 1in Fig. 5 are combined to form packets for `the outer ring coils or phases, whilst a plurality lof the sheet elements shown in Fig `6 are adapted to form the packets t'or the middle phase. T-Wo paths through the armature for the magnetic lines leaving a pole Vof the inductor present themselves, which paths are symmetrical to the radial plane passing through 'the rcentre `oi" the pole. To Athis en-d halt of each packet or bundle on each ring coil yis bent to one side of the centre of the pole when looking at the circumference, and the other half is bent to the other side of the centre 'of the pole.

The path 4ot :the magnetic lines of each magnetic circuit `in `each phase is 'therefore the following: The magnetic lines pass from the pole heads of the straight Shanks of Athe lplate bundles through the air gap into the armature and divide into two symmetrical branches which `flow through the armature 'over 'the pole pitch in ktwo circumferential directions that are opposite t'o `each other, whereafter they return through the air gap yto 'the pole iheads of y'the bent AShanks and complete the magnetic circuit "by 1flowing through the inner fpart of each plate. In "this 4manner the `:armature is permeated magnetically along the whole ot its circumference but only with a mag netic luxrof half the rstrenvth of a pole.

Wvith arrangements accort ing to the present invention, i. e., with the symmetrical distribution ot the magnetic Alines oit each pole of a ring coil, a much better utilization of the materia-l in the armature, i. e., ot' the iron and of the conductors, is obtained than with the above Lmentioned `one sided iiow ot' the magnetic lines.

The packets 'of' sheets '7a. T and 8, 8" are then placed over the ring` coils t, j" and tic respectively Aso that the ring coils occupy the 'itree space 16 of the sheet elements and packets.

A Ybush 9.() is concentrically arranged to the shaft and fixed by means of a disc `18 of 'an angular cross-section screwed Vto the bush to the side part of the casing Apertures Q1 'tor ventilation purposes are provided along the circun'ii'erence of the bush 20. This disc 1S and its outer cylindrical wall 28 enclosing 'thepackets "i" being provided with projections 19 that engage. with the recesses 17 ot' the packets ot' sheets. Q3 antlQLl'denote two discs that are Vfitted to the bush 2O.` 26 is a disc ot' angular cross-section similar lto disc 18 which encloses the packets Ta'and 7b. The packets 8, 8b forming the middle phase are arranged between the discs 23 and 24. 'The discs 23, le and 26 are provided with projections 19 for engagement with the notches 17 ot' the packets. l1 ring nut 27 is screwed onto the bush Q0 for pressingthe disc 26 against the packet. The ring coils 6, 6, (lc together with the packets ot' sheets mounted thereon are consecutiifely assembled on the bush 20 and pressed firmly together by means ot 'the disc 26 being tightly screwed against the packet. Between the adjacent heads of the packets of magnetic sheets wedge shaped distance pieces 28 ot' non-1nagnetic material are inserted for fixing the packe-t heads. i. e. the pole faces in position. The distance pieces z8 are secured by `means of screws .29 to the discs I`23 rand-2st respectively. The packets forming one phase can 'be subdivided by press-Spahn insertions 30 to avoid yeddycurrents -as has been shown for one phase in Fig. 2 of the drawing.

rlhe three ring coils are each connected to one phase of the lthree-phase current .system and alternating fields are generated in a known manner.

Instead of designing the indurtor as stutor, i. e. as the stationary part, it iii-ay be secured as rotor to 'the shait and -the armature may vact as stator and is in this 'ase connectedtotthe casing.

lFigf of the drawings illustrates a developed diagram of the pole face formed by the heads of the packets otmagnetic sheets of the inductor. As may be seen from the lIIU drawing each pole face ofv each phase is composed of the heads of .four packets, which are so located that in between two adjacent heads of one phaseone head of a packet of each of the other two phasesis inserted. rlhe thick full lines represent the bundles of one of the outer phases, the thick dotted lines indicate the laminae or bundles of the other outerphase and the thin full lines denote the laminas or 'bundles of the inner phase, the third phase. The headsof the packets of magnetic sheets forming the alternating pole face aresymmetrically distributed, so that the heads ofthe packets or bundles 'of magnetic sheets of onering coil are arranged infbetween the heads of the packets of the other two ring coils. n

The inductor shown in Fig. 4 is an eight pole inductor. For each ring coil i. e. for each,r phase four bundles of lan'iinae or pact:- ets 7 and four. packets 7b symmetrically arranged to the former but bent in the opposite direction areprovided. In thisiigure the ring coils and the packets 7, and 7" surrounding the ring coils 4are illustrated; in the lower half of Fig. 4 only the packets of an outer face with the long and sharply bent shanks 12 that pass above the coil are shown in full lines, while the Shorter shanhs 11 that pass below the coil are shown iu dotted lines. In the yupper half ofpFig. 4t the pac its of all three phases that are distanced ti( nach other by means of tl'iewedge shaped dista-nce pieces 28 are illustrated. The thin lines represent therein the packets 8, 8b of the middle phase, the thick lines and the dotted lines indicate the packets 7a, Tb, 9a andQf respectively of the two outer phases, whereby centres of the polepieces of the individual Wmme.

phases are at a distance from eachother that equals to one third of the pitch of the pole pieces. v

In order to take into consideration the thickness of the ,packets Y, 7b, 8, 8l the single sheets of which are preferably stamped with adi'ethe Shanks 12 with greater length have to be bent to a very small ra-- dius of curvature to avoid that some of the sheets project beyond the end faces,

In Fig. 7 the diagrammatic development of the pole heads 14, 15 of three magnet sets, the heads tapering in the axial direction is shown; illustrating the cyclic sequence of the phases, assuming the pate bundles to be arranged as illustrated in Fig. 4. It may be seen from this figure the` manner in which the pole heads of the outer and innerrniagnet sets overlap. Inorder to. reduce .the leakage lines from poleto pole and' to improve the power factor an appropriate overlapping is desirable, which is attained at the tapering portionsof the pole heads. n

Single phase motors may be designed in exactly the same mannerk as has Vbeen hereinbefore ydescribed for the three phase motors.

Mmmm. .4...

By suitably changing'the connection of the magnet sets the motor connected to the three phase system can be worked as a one-phase motor ruiming at a speed and giving an output that is reduced .approximately in the ratio of 3 :1 as compared with the motor working as three-phase motor. rIhis changing of the connection can be carried out in a simple manner when the motor is connected to a three-phase system having a neutral wire.

The principal advantages of an alternating motor built according to the present invention are the following:

The winding is simpler and cheaper than the hitherto known constructions as it can be simply wound on a drum in contradistinctionv to the usual bar winding and former-winding that requires exact manual labour.

Motors of this type are very light and are therefore well suited for portable constructions.y Induction motors running at low speeds may advantageously be built accord-y ing to the invent-ion and are much smaller than the hitherto known constructions which necessitated large diameters of the inductor and of the armature owing to the high nmnber of slots required for multipolar motors. The design according to the invention particularly ada-pts itself to slow speed small motors.

I claim:

l. In an alternating current machine, three sets of magnets consisting of packets of magnetic sheets and three separate coaxially arranged ring coils for exciting said magnets,the packets of magnetic sheets of each magnet being symmetrically arranged to the centres of the pole pieces in the pole faces and the magnets of the individual sets being so closely located that the heads of the packets forming the pole faces of one set of magnets are arranged between the heads ofthe packets of the other sets, forming l thereby a substantially uniform concentric polar surface and an armature memberfwith appropriate symmetrically` spaced exciting windings, said armature being within the magnetic field of the magneticl element.

2. In an alternating current machine, three sets of magnets consisting of packets of magnetic sheets each element of the sheets forming said packets being made of one piece, and three separate coaxially arranged ring coils for exciting said magnets, the packets of magnetic sheets of each magnet being symmetrically arranged to the centres of the pole pieces inthe pole faces and the magnets of the individual sets being so located that the heads of the packets forming the pole faces of one set of magnets are closely arranged between the heads of the packets of the other sets, so as to form a can polar surfaces ofthe 1" lili) Substantially uniform polar surface',V with an armature having appropriate symmetrically spaced windings.

3. In an alternating current machine, three sets ot' magnets consisting or" packets ot' magnetic sheet-s, each clement ot'` the sheets forming said paclrets being made of one piece and having tapering extended parts forming the heads of thev packets', and three separate coaxiall'j,v arranwed ring coils 'i'or exciting said magnets, the packets of magnetic sheets of each magnet beingV symmetrically arranged to the centres of the pole piece-s in the pole `faces and the magnets of the individual sets being so located that the heads or' the packets consisting ol said tapered extending parts ot' the sheet elements and forming ,the pole faces of one set of magnets are arranged between the heads ot the packets or' the other sets, the

tapering extended parts of the' sheetelements of the respectivev sets over-lappingv each other to an appropriate amount to reduce the leakage. f

at. In an alternating' current machine, three sets of magnets consisting' ot packets of magnetic sheets and three separate coax'ially arranged ring coils Jfor exciting said magnets, the packets ot magnet-ic sheets ol"r each magnet being symmetrically airanged to the centres of they pole pieces-in the pole laces and the magnets ot the individual sets being so located that the heads ot' the'packets forming thepele faces of one setof magnets are arranged between the heads of the packetsv of the other sets,v and a bell shaped armature enclosing the indue-tor and acting as rotor.

5. An alternating` current single or multipliase machine comprising concentrically arranged- (with relation to the axis of the machine) exciting coils, for each phase, contained within appropriate magnetic bodies, the pole pieces of said bodies excited by each set of coils being symmetrically arranged between the pole pieces of the other setsand forming'substantially uni-form circumferential polar faces', anda rotor or armature element with appropriate symmetrically spaced exciting windings arranged within the magnetic field of the stator element.

6. An alternating. current single or multiphase induction machine, comprising concentrically arranged (with relation to the axis oi" the machine) exciting coils, for each phase, contained within appropriate magnetie bodies, the pole pieces of said bod-ies excited by each set of coils being symmetrically arranged between the pole pieces of the other sets and forming substantially uniforml circumferential polar faces, andan exterior armature or rotor member having symmetrically spaced closed induced win'd ingswithin the magnetic field ofthe stator.

In' a three phase alternating current 1nachinc,fanl inductor comprising three sep'- arate coaxially arranged ring coils, one for each phase, and a set of packets of magnetic sheet-s arranged around each ring coil and provided with pole heads forming an alternating pole'iace that is concentric to the axis of thel machine, and an armature; one half el' each packetY of magnetic sheets on each ring coil being bent to one side and the other halt` to the other side when looking at the pole piece face, whereby the magnetic lines leaving a pole piece have' two paths through the armature that are" symmetrical to the radial plane passing through the centre of the pole piece.

S. In a three phasemachi'ne, an' indu'ctor comprising three separate coaxially' arranged ring coils, onel for each'` phase, and a set of packets of magnetic sheetsarranged around each ring coil andprovidfed with pole heads forming an alternating pole piece face that is concentric to the axiso the machine, and an outer armature, one' haltI of each packet of-magnetic sheets on' each ring coil being bent to one sideA and the other half to the other sideV when' looking at the pole piece face,A whereby the mag# netic lines leaving a pole have two paths through the armature that are symmetrical to the radial plane passing through the' centre of the pole piece'.

9. In a three phase machine, an inductor' mature rotor, one half of each'paclret of' magnetic sheets on each ring coil being bent to one side and the other half to the other side when looking at the polepiece" face, whereby the magnetic linesl leaving a pole piece have two paths through the armature that are symmetrical to the radial plane passing through the centre' of the pole piece.

l0. In a three phase machine, an inductor comprising three separate'coaxi'ally arranged ring coils for each phase, and' a set' of packets of magnetic sheets arranged around each ring coil and provided with pole heads forming an alternating pole piece face that is concentric to the axis of' the machine, and an outer armature, the magnetic sheet elements forming the'packets being made otone piece and comprising an inner part to which Shanks join which carry the pole piece heads, one' haltof the elements of each packet on each vring coil beingfbent to one sidek and the other half to the' other side when looking y at the pole pieee'face, whereby the magnetic lines' leaving a pole piece have two paths through the armature that are symmetrical to the radial plane passing through the centre ot the pole piece.

11. In a three phase machine, an inductor stator comprising three separate coaxially arranged ring coils, one for each phase, and a set of packets of magnetic sheets arranged around each ring coil and provided with pole heads forming an alternating pole piece face that is concentric'to the axis of the machine, and an outer armature rotor, the sheet iron elements forming the packets being made of one piece comprising an inner part to which Shanks join which carry the outer pole piece heads, the latter being tapered'in the axial direction so that the pole piece heads in the cyclic sequence overlap to an appropriate extent for reducing the leakage, one halt of the elements of each packet of magnetic sheets on each ring coil being bent to one side and the other half to the other side when looking at the. pole piece face, whereby the magnetic lines leaving a pole piece have two paths through the armature that are symmetrical to the radial plane passing through the centre of the pole piece.

In testimony whereof I affix my signature.

HEINRICH FREI. 

